[all-commits] [llvm/llvm-project] 5c68a1: AMDGPU: Make various vector undefs legal

[Matt Arsenault via All-commits]

  Branch: refs/heads/release/15.x
  Home:   https://github.com/llvm/llvm-project
  Commit: 5c68a1cb123161b54b72ce90e7975d95a8eaf2a4
      https://github.com/llvm/llvm-project/commit/5c68a1cb123161b54b72ce90e7975d95a8eaf2a4
  Author: Matt Arsenault <Matthew.Arsenault at amd.com>
  Date:   2022-11-01 (Tue, 01 Nov 2022)

  Changed paths:
    M llvm/lib/Target/AMDGPU/SIISelLowering.cpp
    M llvm/test/CodeGen/AMDGPU/commute-shifts.ll
    M llvm/test/CodeGen/AMDGPU/cross-block-use-is-not-abi-copy.ll
    M llvm/test/CodeGen/AMDGPU/dagcombine-fma-fmad.ll
    M llvm/test/CodeGen/AMDGPU/extract-subvector-16bit.ll
    M llvm/test/CodeGen/AMDGPU/insert_vector_elt.ll
    M llvm/test/CodeGen/AMDGPU/select-undef.ll
    M llvm/test/CodeGen/AMDGPU/skip-if-dead.ll
    M llvm/test/CodeGen/AMDGPU/v1024.ll
    M llvm/test/CodeGen/AMDGPU/vgpr-tuple-allocation.ll
    M llvm/test/CodeGen/AMDGPU/wqm.ll

  Log Message:
  -----------
  AMDGPU: Make various vector undefs legal

Surprisingly these were getting legalized to something
zero initialized.

This fixes an infinite loop when combining some vector types.
Also fixes zero initializing some undef values.

SimplifyDemandedVectorElts / SimplifyDemandedBits are not checking
for the legality of the output undefs they are replacing unused
operations with. This resulted in turning vectors into undefs
that were later re-legalized back into zero vectors.

(cherry picked from commit 7a84624079a2656c684bed6100708544500c5a32)